Most genes in higher cells and their viruses contain non-coding intervening sequences. These sequences are removed from primary RNA transcripts via an excision and religation process called RNA splicing. The mechanism by which splicing occurs or its role in regulating ekuyaryotic gene expression is unknown. I propose to investigate a number of different aspects of RNA splicing in the transformation region of the adenovirus, type 5 genome, region Ela. Mutants will be isolated containing specific alterations within this region and the affect of these alterations on splicing determined. This system is particularly well suited for such a genetic approach primarily due to the existence of a complementing system where mutants can be isolated and grown regardless of whether the products encoded by the spliced messages are rendered defective or not. The different aspects that will be considered are: (1) The role of nucleotide sequences around splice junctions in providing specificity to splicing. (2) The role of RNA conformation in specificity and regulation of splicing. (3) The role of splicing in the stability and/or transport of message. (4) The mechanism and regulation of the synthesis of overlapping RNA differential splicing of a common precursor.